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Tuesday, September 25, 2012

Agave Dying Suspected Overwatering But...

Q. The Agave in my front yard (maintained by HOA) is dying.  I was informed by an Aborist that it was getting too much water.  I relayed this to the HOA maintenance and when they looked at it they said it needed more water and ran another dripper line, which drips about every day. Can this once beautiful plant be saved. Pictures are 6 weeks apart and show how it has deteriorated.

Agave appearing to wilt from a watering problem, or is it?
This could also be from the agave weevil.

A. This is either too much water or agave weevil damage. The weevil deposits eggs in the crotches of the leaves at the base and the eggs hatch. The larvae of the weevil then invade the roots where they feed causing the agave to collapse just like in your picture. However, overwatering can cause the roots too rot easily and cause exactly the same type of symptoms; collapse of the outer leaves and eventual death of the entire plant. Unfortunately you get the same result and is not much you can do at this stage.
            I would predict the plant will die and it will have to be removed. American agave is probably one of the worst ones for agave weevil infestation. Replanting with a different agave like
Agave weevil in the roots of an agave. It is a light colored
or white grub near the center of the picture.
            Weber’s or Parryii will be more resistant to the weevil but not overwatering. Both of these are smaller and more in scale with homes landscapes.
            There are two types of overwatering. One is watering too much and the other is watering too often. This is more of the watering too often kind of problem. Wish I had a better story to tell.
            I have attached a brochure from the U of Arizona on this weevil problem and some recommended preventions from one of the arboreta down there. I also attached a picture of the weevil larvae you would find in the roots if that was the cause. They would be there now.

Papaya Growing By Accident. Can I Keep It?

One type of papaya. Fruit are borne on the
trunk like so many tropical fruits.
Q. I accidently have a papaya tree growing in my yard.  When we moved in I setup a compost bin.  Unfortunately I didn’t think about the irrigation pipes when I placed the bin and I eventually had to move it to fix a leak.  My wife had a thing for papayas while pregnant so quite a few papaya seeds went in to that bin prior to me moving it.  After moving the bin one of the seeds sprouted.  I didn’t know what it was at first and just let it grow out of curiosity.  My wife eventually identified it and, since I now knew I was growing a tree right on top of a pipe, I had to move it as well.  That barely succeeded and it almost died but eventually made a comeback and is now thriving at two feet tall.  Now I’m concerned about getting it through the winter which brought to mind your article in the weekly and I thought I would bounce the concern off of you.  I’m thinking about building a simple green house from sheet plastic and pvc pipe.  Would that work or should I take a different approach?

A. Very interesting story. Yes, I have encouraged people to consider papaya in Las Vegas because there are some varieties like the Hawaiian Solo types which are highly productive and some can bear fruit nine months after planting from seed. You can find seed sources online and refer to this website for growing instructions in mild climates.


They will grow in the Phoenix area as evidence on this website
Papaya in container
For our area the two enemies will be climate and soils. So you will have to modify both of these if it is to work. In the temperature end you have to consider the heat as well as the cold. I would pick a location in the yard that has some protection from the late afternoon sun as much as possible.
            However the plant will need lots of sunlight so make sure it gets it in the morning hours up to mid-afternoon. Winter cold will kill it for sure. So it will have to be protected from windy locations and a structure put over the top during night time.
            This structure could be opened during the day when temperatures are above 50F. Throw a blanket or protection over it when it gets cold at night. The papaya is a tree that grows straight up  so you will not be able to keep it very long before it is too tall. So plant in succession or even annually.
            Next is soil modification. The soil must drain easily and add lots of compost and phosphorus based fertilizers at planting time. This could be a lot of fun for you to try.

Weed Control in Lawn of Spurge

Q. Our Association Lawns are infested with a weed that spreads rapidly. We have been told it is spurge. Some owners have been told by a nursery that spurge control is accomplished by spraying in June and approximately every 6 weeks through the summer. Others have said that spraying can't be done when it is very hot. Please give your opinion on this matter.

Prostrate or spreading spurge
A. If this is spurge you are fighting it is a very poor competitor with a lawn. Most of it can be kept out by increasing the competitiveness of your lawn by following a few rules:

           Keep the lawn dense by keeping its fertilizer program current.

           Make sure it is getting water at the right times and avoid stress during the summer months and starting in February for spurge.

Closeup of the small leaves of a spotted spruge. Not all spruges have
spots on their leaves but all spurges have white sap or latex. So if you
want to know if your weed is a spurge, break the stems and look for the
white sap or latex.
           Irrigation system must apply water evenly to the turf area. Get rid of mix and match nozzles and make sure the system applies water head to head.

           If this is fescue, all irrigation heads must pop up out of the ground a minimum of four inches. Replace irrigation heads that are less than this with four inch popups.

           Do not use line trimmers to trim grass around irrigation heads or along hard surfaces like sidewalks.

Use a steel edger, not line trimmers to edge turfgrass areas.

           Mowing height must be 2 ½ inch minimums.

           You can use post emergent herbicides (weed killers applied after you see it up) such as Trimec or similar but the best weed killers are applied pre emergent, before the seed germinates in the spring. Visit Helena chemical in town to get your chemicals and visit with them about which chemical has been working best and the timing of it. Do it this winter before spring.

Controlling Bermudagrass Growing in.....

Common bermudagrass stolons creeping from the
lawn over a sidewalk. Hybrid bermudagrass
is much more restrained in its growth.
This is a queston frequently asked, "How do I control bermudagrass in......" so let's talk about it.

The big problem is common bermudagrass. It is spread by seed, underground stems called rhizomes that can grow under the surface of the soil for many feet and re-emerge in a new location. Sort of like "Whack-A-Mole". You pull it or spray it here only for it to popup over there. Below ground the bermudagrass cannot get the energy it needs from sunlight. It must rely on food supplies sent by the mother plant growing in sunligh OR live off of stored food in its stems.

It can also spread by planting, or accidentally planting, any of its stems above or below ground. For instance you can take the above ground growth, cut it up into small pieces, throw it on the ground, water it and it will start a new plant any place these cut up pieces fall. When we WANT it to spread like this, we call are planting by stolons or "stolonizing" the area. The hybrid bermudagrasses, the kind that are nice to grow like on golf courses, is planted exactly this way.

The underground stems that spread the mother plant to a new location all by growing underground are called rhizomes. The only difference between the above ground stems (stolons) and the below ground stems (rhizomes) is there location AND their propensity to either grow above or below ground. What you can do to stolons, you can do with rhizomes essentially. So if you cut up a bunch of rhizomes the same way as stolons and spread them on the soil surface, guess what will happen. You got it. You have a new lawn whether you wanted it or not.
Hybrid bermudagrass stolon (left) stem and
leaves (right) and rhizome (bottom)

Question for YOU. What will happen if you rototill a bermudagrass weed area in the hopes of getting rid of it?
Answer: You spread it.

So how do you get rid of bermudagrass weeds? You exhaust it. You kill it, let it grow a bit, kill it again, let it grow, kill it again, let it grow, kill it again...... In this way you begin to exhaust its stored food supply AND by constantly killing or cutting off its access to sunlight you deny it the ability to put more stored food into its food supply. In the end you exhaust it, weaken it and it dies.

You can deny it sunlight by constantly killing top growth back as soon as it gets exposed to that life-giving light a week or so. You can kill the top growth by mechanically whacking it off to soil level or below or killing it to the ground with a poison such as Roundup or even vinegar. Anything that will cause it to die to the ground and not hurt the surrounding environment. The advantage of Roundup is that it is systemic and will travel into the ground a distance and kill somewhere below ground level. To grow back requires more energy and so it will be more effective than just whacking it off or killing the tops.

The disadvantage is that it is a weed killer and it may have some adverse side effects. Other chemicals to look at include Poast and Fusilade which are also systemic weed killers and are potentially less damaging to surrounding plants.

Nothing wrong with a hoe, shovel and other tools that will help take it to the ground. Regardless, the secret to success will be to stay on top of it and never let it grow back more than a few inches before you knock it down again.

Praying Mantis Eggcase Confuses Reader

Praying mantid (mantis) egg case from reader.

Q. I would like to know what this was on my Royal Blenheim apricot tree in my backyard in North Las Vegas. It appeared to be hard and had circular markings on the part attached to the tree as thought it was an egg casing. I removed it and hopefully it was not a helpful insect. You may use the picture as you wish.

A. It looks like a mantid egg case to me. Please be careful. These are good guys and in the future leave the egg cases where they are or move them to a location where they will find lots of food and help you beat the bad guys.

Praying mantis (mantid) released on to sweet acacia to
battle cicadas.


Watering Citrus in Bullhead City

This is an irrigation basin around a fruit tree. The basin keeps
water contained near the tree where the roots are. This basin
receives its water from a bubbler (upper left inside the basin).
This particular bubbler puts out two gallons per minute if the
water pressure is adequate or above (it is pressure
compensated which means if the pressure is higher than
adequate it will still give only 2 gallons per minute)
I have three trees  planted in a “L” shape with the orange and lime on the bottom of the “L” and a lemon on the top. They are about 6 years old and the trunks are about 5” in diameter. They are almost 6 ft. tall and about 7 ft. in diameter. I have the three on a separate circuit with each having a 1/2 “ p.v.c. bubbler providing water every other day at 6:30 a.m. and 8:30 p.m. for 15 minutes. this fills a water well that is about 4” deep and 4 ft. across for about 10 minutes after the water goes off. The water is then absorbed into the ground.
            I have tried to let the water run longer but it seem's to want to go outside of the well and not deeper into the well. I thought about cutting down on the flow so it would run longer and maybe soaked in to the well better but I have not tried that. I have been told to water once every 90 days and let it run for 3 hours. I would have to cut the bubblers just to a drip or it would flood the yard. I don’t know what is the best option. I get a heavy crop of limes now but just a few oranges, and they are half orange and half green. any suggestions?  Remember this is in Bullhead City and it gets very hot during june thru sept

A. I forwarded your question to Terry Mikel, retired Extension Horticulturist with the University of Arizona out of the Phoenix office who knows your location very well. Here it Terry's response:

I am familiar with much of the Bullhead City soils and conditions but I have yet to hear that watering every '90' days  . . . I should think, or hope someone might have meant or you meant every '9' days .. . That would be certainly a point of clarification . .
Irrigating citrus in Hermosillo, Mexico, at USON's research
farm. This is ditch irrigation which is terribly inefficient but
still more efficient than flooding the entire field.
Water moves toward the roots from the ditch
through the soil. The most
efficient would be drip irrigation and would not need a basin
or ditch but is expensive for farmers with hundreds of acres.

            I personally avoid giving calendar or numerical days for watering . . There are too many factors; for example, are you near the river with a heavy clay soil or up on the higher ground where the soil drains much better? . . .

            It sounds like you are careful and meticulous about watching the growth and you should check the soil in the morning hours and water when it is dry down a couple inches . .  .Remember to check in the morning not in the afternoon when the heat will dry all soils there down a couple inches . . In the morning the soil will have the cooling  of the night to percolate water up from below thus rehydrating (fancy word for wetting) the upper soil zone . . . If you want to add more water and much more efficiently then change how you add the water . .

Set the repeat cycle to  whatever time it takes the initial water to move into the soil and then run the set again instead of spacing it out for hours . . This is called surge watering and it works much better than the delay . . . Maybe next summer you can try and see if you can go more days between waterings without impacting the plant . .

If you have a fast draining soil it might not work; likewise, if your soil is heavier you might . . . Don't forget that a nice thick layer of mulch on the soil surface saves a lot of water from being lost into the air through evaporation . . .

There are some great Master Gardeners in your area that are both knowledgeable and grow lots of things under your conditions . .

With respect to the lime's yield vs. the orange's yield:  My first guess is the orange is a Navel type orange . . They are notoriously sensitive to hot dry condition and their fruits drop like flies . .

The plant itself does well but the fruits you get are great but the number you get is usually a disappointment . . .It's almost a shame they are sold . . .

Terry Mikel